T111 Insights from Microfossils, Palynology, and Their Modern Analogs: From Traditional to Emerging Techniques (Posters)

Monday, 5 November 2018
9:00 AM - 6:30 PM
Halls J-K

IMPACT OF ANTHROPOGENIC POLLEN CHRONOHORIZONS ON AGE-DEPTH MODELS FOR THE ATLANTIC COAST OF THE UNITED STATES DURING THE LAST 500 YEARS

Paper number: T111-15
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

Vegetation response to anthropogenic modification has been reconstructed at many locations. Synthesizing observations from multiple locations improves our understanding of the regionality of these impacts and drivers. Human alterations of plant communities vary spatially in timing and overall impact. Anthropogenic impacts, including deforestation associated with the introduction of European-style agriculture and the introduction of non-native plants, are observed in the pollen record and serve as useful markers of time for a specific region. For example, the abrupt increase in Ambrosia pollen in the mid-Atlantic corresponds to 18th Century deforestation. By applying these dates to changes in pollen abundances observed in saltmarsh cores, we can improve composite chronologies and the accuracy and precision of age-depth models.

Here, we combine new and published pollen data from Florida to Connecticut to determine how pollen chronohorizons impact the precision of age-depth models. We analyzed pollen assemblages from nine locations along the Atlantic coast of the United States, including new reconstructions from the Florida Keys, Delaware Estuary, the Chesapeake Bay in Maryland, and northern New Jersey. All pollen assemblages are placed in a geochronological framework using composite chronologies of radiocarbon; pollution histories for contaminants such as lead, nickel, and chromium; and 137Cs.

Due to a plateau in radiocarbon ages between 500 and 150 years before present, and lack of pollution markers before approximately 120 years before present, there is a geochronological gap. This gap contains several widely-researched events, such as the Little Ice Age and the start of modern climate change in the late 19th Century. Pollen chronohorizons can be used to fill in this gap and better constrain chronology. We identify which pollen chronohorizons improved the precision of age-depth models and determined ways in which others might be improved. Pollen improved the precision of age-depth models in some case by more than 100 years. Our data demonstrate that the geochronology can be significantly improved by developing location-specific pollen chronohorizons.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-322616

© Copyright 2018 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.